In recent years, an easily portable, small-size projector capable of displaying a large-size image is vigorously developed. For example, a video camera incorporating a small-size projector connectable, for instance, to a notebook computer or a projector capable of projecting a recorded image is now commercially available. It seems that a projector will be incorporated into mobile phones and smartphones in the future.
A projection image display device is known as a projector that uses a light-emitting diode as a light source instead of a conventional lamp-type light source. It is expected that such a projection image display device will be deployed as a head-up display. The head-up display is mounted, for instance, in an automobile due to its high-luminance image display capability to project an image onto a windshield for navigation or other purposes. Light-emitting diodes have advantages over lamps of being longer life and consuming less power. Meanwhile, the light-emitting diodes, particularly red ones, significantly decrease its light intensity when a temperature rise occurs.
The projection image display device produces an image by mixing red, green, and blue light. If the intensity of red light lowers due to a temperature rise in a red light source during the use of the projection image display device, the intensities of green light and blue light have to be lowered in accordance with the intensity of red light. This causes a problem in which a bright image cannot be maintained for a long period of time. In order to maintain a bright image in the above circumstances, it is important that the temperature rise in the red light source be reduced to suppress a decrease in light intensity.
A method of dissipating heat through a heat sink is disclosed in Japanese Unexamined Patent Application Publication No. 2010-177076 in order to address the above problem. The disclosed method transfers heat generated from a light-emitting diode (LED) circuit board to a frame through a heat sink for the purpose of preventing an LED temperature rise.